1967 Fender Bassman Question - Power Supply Issues

[Tony Bones]

Removing the secondaries from the PT at the input connection at the rectifier/bias board, the PT draws little to no amps. The light bulb limiter stays very dim.

Wait, are you saying that with the HT secondary wires disconnected, the light bulb lights up at all? It should not be very dim, it should dark. Nothing at all.

Even a "very dim" bulb indicates some current. Where is that current going? The bias circuit? that shouldn't be enough to light the bulb, not even very dimly.

[nosaj]

Wait, are you saying that with the HT secondary wires disconnected, the light bulb lights up at all? It should not be very dim, it should dark. Nothing at all.

Even a "very dim" bulb indicates some current. Where is that current going? The bias circuit? that shouldn't be enough to light the bulb, not even very dimly.

Let's be clear when someone says disconnect the secondaries that means all windings HV, Bias, Filament.

[g1]

He said he disconnected the secondary wires to the rectifier/bias board. Near as I can tell, that means the heaters are still running.

[Tony Bones]

He said he disconnected the secondary wires to the rectifier/bias board. Near as I can tell, that means the heaters are still running.

Tubes have heaters? I should probably be banned.

[nosaj]

Tubes have heaters? I should probably be banned.

Ok but are you sure?

Nosaj

[Helmholtz]

Wait, are you saying that with the HT secondary wires disconnected, the light bulb lights up at all? It should not be very dim, it should dark. Nothing at all.

Even a "very dim" bulb indicates some current. Where is that current going? The bias circuit? that shouldn't be enough to light the bulb, not even very dimly.

Even with ALL secondary wires disconnected, there is still the magnetizing current of the PT which can make even a 100W bulb light dimly.

[Tony Bones]

Even with ALL secondary wires disconnected, there is still the magnetizing current of the PT which can make even a 100W bulb light dimly.

Well, that was probably not the last time I'll say something stupid.

Stay tuned!!

[keithb7]

Diodes arrived today in the mail. Immediately rebuilt the board with all new diodes. Replaced non-functioning stand-by switch. Amp plays and sounds awesome. I'll clean up a few things, spray the pots, set the bias and send it back to its owner.
Thanks for the tips folks. Power tranny was spared...Whew! That'll never happen again on my watch.

Great members here, great forum. Thanks again.

[SoulFetish]

Even with ALL secondary wires disconnected, there is still the magnetizing current of the PT which can make even a 100W bulb light dimly.

yup